Filter elements, having media packs of pleated paper or other appropriate materials, are commonly used on over-the-road trucks, agricultural, automotive and off-highway equipment for preventing dirt, dust, and moisture from entering machinery, such as an engine or an air compressor, with the incoming air supply. In one popular style of such filters, the filter element includes a tubular-shaped media pack having an open end, configured to tightly engage a pipe or conduit supplying air to an engine, with the opposite end of the tubular-shaped media pack being closed by a closed end cap. Typically such filter elements are mounted in a housing, in such a manner that air flows through the filter element in an outside-in direction. Contaminants in the air stream are removed as the incoming air flows through the media pack. Often, the closed end cap includes one or more compliant ribs for aiding in properly positioning the filter element within the housing, and/or for providing additional structural and sealing functions at the juncture between the filter element and the housing.
In the design of such filter elements, a number of factors must be considered. Generally such filter elements must be produceable at low cost, so that they can be replaced, without significant expense, at regular intervals. It is also desirable that such filter elements be constructed in such a manner that they are readily incinerable or recyclable.
In addition to being produceable at low cost, in a manner that is readily disposable or recyclable, it is necessary that the filter element be designed in a manner which is structurally efficient and effective, so that the filter element can withstand the considerable forces to which the elements may be exposed during operation. As the filter element becomes increasingly plugged with contaminants removed from the incoming air, the pressure drop across the tubular-shaped media pack increases. The filter element must be constructed in such a manner that it can withstand inwardly directed forces, caused by the increased pressure drop, to preclude having the media pack be deformed inwardly when the media pack has absorbed its maximum rated capacity of contaminants.
The radially inwardly directed force of the incoming air, as the filter media pack becomes increasingly dirty, can also cause problems in maintaining the radial seal between the filter element and the pipe or conduit supplying air to the engine. Commonly assigned U.S. Pat. No. 6,447,567 B1, to Ehrenberg, the disclosure of which is incorporated herein in its entirety, discloses an air filter element having an integral radial seal gasket which is particularly well suited to maintaining the radial seal under demanding operating conditions. Specifically, Ehrenberg '567 includes a substantially stiff insert ring, which in combination with an inner liner provides improved resistance of the media pack to inwardly directed forces.
Ehrenberg '567 also discloses forming both an open and a closed end cap, at opposite ends of a tubular-shaped media pack, from foam materials, in a manner which is highly conducive to low-cost manufacturing of filter elements. Specifically, Ehrenberg '567 discloses a closed end cap formed entirely of a molded polyurethane material extending over the ends of an inner and outer liner and into the end of the media pack, thereby providing a configuration which is highly manufacturable. Although the one-piece, molded end cap of Ehrenberg '567 provides a highly efficient and effective structure under most operating conditions, for applications where the inwardly directed air forces are substantial, and/or applications where the inner diameter of the tubular-shaped media pack is of a large size, a one-piece end cap, as taught by Ehrenberg '567, may not provide sufficient strength.
One approach to providing additional strength in a closed end cap is illustrated by U.S. Pat. No. 5,484,466 to Brown, et al., which discloses reinforcing the closed end cap of a filter element with a plate, or pedestal of metal or stiff plastic. Although reinforcing a closed end cap of a filter element with a plate or pedestal of metal or stiff plastic, as disclosed in Brown '466, is highly effective in strengthening the end cap, the addition of the reinforcement undesirably increases the complexity and cost of producing a filter element.
It is desirable, therefore, to provide an improved filter element, and a method for making such an improved filter element, having additional resistance to operational loads on the filter element, without the use of additional reinforcing plates to the closed end of the filter element.